1. Field
One embodiment of the invention relates to a printed circuit wiring board having a flexible flat cable, as well as to an electronic apparatus having electronic components connected to the printed circuit wiring board by means of the flexible flat cable.
2. Description of the Related Art
In order to reduce contact resistance and make electrical continuity superior, a copper wire which has been subjected to, e.g., tin-lead plating has hitherto been employed as a conductor to be used for a flexible flat cable. From an environmental viewpoint, nonuse of lead for various wires which are to be used in electronic equipment is desired. For this reason, applying a copper wire, which is plated with lead-free tin or a lead-free tin alloy, even to the conductor used in a flexible flat cable has been examined.
Even when the lead-free tin plating layer or the lead-free tin alloy plating layer is oxidized to thus form an oxidized tin film on the surface thereof, the oxidized tin coating film is easily rubbed off by means of friction or the like, which arises in a mating section, so that electrical conductivity is readily achieved. However, when the flexible flat cable that employs the copper wire plated with tin or a tin alloy is fitted to the connector, metal crystal—which grows into the shape of whiskers as a result of extrusion of metal molecules of a plated coating surface—, so-called whiskers arises by means of the stress exerted on the fitted portion to thus raise a possibility of occurrence of a short-circuit between conductors (see, e.g., JP-A-2005-48205).
When phosphor bronze plated with, e.g., lead-free tin or a lead-free tin alloy, is used as a contact section of a connector to be connected to a flexible flat cable, there occurs a problem of analogous whiskers arising in the surface of the contact as well.